There is no such thing as a "proof" in the scientific or historical community, just bodies of evidence. Only in the world of math is there such thing as proof, and we aren't trying to solve a mathematical problem here.

This body of evidence is very strong. Footage would make the body of evidence even stronger but it isn't necessary, as the body of evidence is already much stronger than anyone who might try and take a stance that such events never happened.

There is such a thing as proof in scientific method actually. A proof is unequivocal evidence. For instance if we can ascertain that the court dimensions and rim height are regulation and we actually see through footage that Wilt dunked from the free throw line that would constitute a proof.

Remember we're not discussing a hypothesis dealing with an all-explaining theory (for theories we cannot prove them we just don't reject them... for example we have no evidence to refute string theory and lots of evidence that goes in its favor but that doesn't make it true as there could be many situations where the theory fails). Here we're simply discussing whether a certain well-defined event - Wilt dunking from the free throw line - happened. With footage and ascertained court dimensions we can PROVE it. Unfortunately for historical events before the age of photography/film there is no such thing as concrete proof only supporting evidence. Not that there is anything wrong with that. Sometimes indirect evidence can be rather overwhelming in favor of something.

Like you said the body of evidence is strong and I'm 99% sure Wilt could do it even without the video footage. That's the bottom line. The rest is you and I discussing the scientific method.